A boiler is a closed vessel in which water or other fluid is heated.The fluid does not necessarily boil.
They can be rented during the construction of the house.
It seems that the least complicated plumbing services are performed in the course of construction of the house, because they are limited to the performance of domestic water supply and sewage, and in the case of apartment blocks need to make a detailed plan of such a network adequate to the number and position of the individual apartments.
In schools, sports can also stand up showers.
Water supply and sanitation has been a primary logistical challenge since the dawn of civilization..Where water resources or infrastructure or sanitation systems are insufficient for the population, people fall prey to disease, dehydration, and in extreme cases, death. Major human settlements could initially develop only where fresh surface water was plentiful, such as near major rivers.Over the millennia, technology has dramatically increased the distances across which water can be relocated, but the availability of clean and fresh water remains a limiting factor on the size and density of population centers, and is expected to remain so into the foreseeable future.Źródło: https://en.wikipedia.org/wiki/History_of_water_supply_and_sanitation